Electronic packages generally include multilayer circuit boards or substrates with a large number of conductive and insulating layers formed thereon and an increasing number of semiconductor chips mounted on one surface of the multilayer board or substrate. The increased number of active elements per chip, although designed with reduced power dissipation, results in an increase in both the electrical power being consumed and the heat being produced. Improved cooling means for electronic packages are needed to keep the maximum temperature of the chips below their maximum operating temperature.
U.S. Pat. No. 4,879,629 discloses a liquid cooled integrated circuit module including a substrate and a plurality of chips mounted thereon. A compliant member, which is hermetically sealed at its perimeter to the substrate, completely seamless, overlies all of the chips. Between the compliant member and the chips, are thermally conductive studs carrying away the heat by conduction from the chips to the compliant member.
An integral heat pipe for transferring heat away from electronic components is described in U.S. Pat. No. 4,833,567. In a sealed chamber around the electronic components a thin film of liquid working fluid is in direct contact with the electronic components. The fluid absorbs the heat generated by the components, and transfers the heat away from the components by thin film evaporation of the liquid.
It is, however, desirable to prevent liquid contact with the chips since the liquid coolant causes stresses on discrete wiring and interior pressures. One possibility to overcome these problems is shown in IBM Technical Disclosure Bulletin Vol. 20, No. 2, July 1977. A plurality of heat sinks is molded into a flexible membrane so that each heat sink can be placed in contact with a chip to be cooled. The coolant transfers heat from the heat sinks to a finned-type cap by natural convection.
In order to obtain low thermal resistance between the object to be cooled and the coolant, good mechanical or physical contact with the object is important. One example where this is achieved is the flexible membrane described above that allows the heat sinks to conform to the chip surfaces for good conductive heat transfer.
To improve the effectiveness of cooling it is desirable to cool the top and bottom side of the module. This is realized in DE-Al-29-38-096 which describes a power semiconductor element arranged in a housing in a self-supporting way. Cooling pipes may be connected to external supply means provided at the top of the housing allowing a coolant to flow through the housing. The isolating coolant flowing through the housing cools the power semiconductor element arranged on a disk from both its sides.